The long-term objective of this nursing science research program is to describe the physiological, psychological, and behavioral factors associated with the symptom of fatigue in men and women with systolic heart failure (HF). Data generated from this study will serve as the foundation for the development of interventions to manage fatigue and improve quality of life in this population. The primary aims of the study are: to describe and compare the symptom of fatigue (Fatigue Severity Index, Profile of Mood States, and Short Form 36 Health Survey) between patients with systolic heart failure and age-matched healthy control subjects, to determine if psychosocial factors such as depression (Hospital Anxiety and Depression Scale) are correlated to fatigue in HF patients, and to determine if increased levels of the cytokines (tissue necrosis factor alpha and interleukin-6, as determined by enzyme-linked immunoassay) are correlated to fatigue in HF patients. The applicant hypothesizes that in men and women with systolic HF, increased levels of proinflammatory cytokines and depression are correlated to the occurrence of fatigue. Proinflammatory cytokines (tissue necrosis factor alpha, interleukin-6) have been implicated in fatigue in HF, but to the author's knowledge, no studies have been published in which cytokines were correlated with self reported measures of fatigue from HF patients. The proposed research will utilize a prospective, cross-sectional study design. A convenience sample will be recruited from a large urban based heart failure outpatient setting. Subjects will be 45 years of age or older and will be diagnosed with systolic HF based on physical exam and diagnostic tests, which reveal a left ventricular ejection fraction of <40%, and are assigned to NYHA classification II-IV. All subjects will be under the care of a board certified cardiologist and will be 45 years of age or older. Age-matched male and female subjects will be recruited from a community setting to serve as a control group. HF and control subjects will complete the Fatigue Severity Index, Profile of Mood States, Short Form 36 Health Survey, and will provide blood samples for cytokine analysis at two time points (baseline and 6-8 days later). The relevance of this research to public health is very high. HF is one of the most prevalent cardiovascular disorders in the U.S., and fatigue is the most debilitating symptom associated with HF. Findings from the proposed study will contribute to the development of future interventions to manage fatigue in HF patients.